1. Technical Field
This invention relates generally to diagnostic medicine, and more particularly to a digital magnetic resonance (MR) method and system for patient monitoring and diagnosis.
2. Background Information
Recall that some magnetic resonance procedures (MRPs) place the patient directly into the bore of a very large superconducting magnet for diagnosis. The magnetic field within the bore produces an equilibrium condition amongst nuclei in the patient's body that brief pulses of radio frequency (RF) energy upset. The nuclei respond to the pulses by changing spin energy states and thereby producing weak RF signals at distinct resonant frequencies that computerized equipment detects and processes for the information conveyed.
Such MRPs proceed noninvasively and without harmful radiation effects, and patients appreciate the absence of needles, contrast agents, and radioisotopes. For many such reasons, MRPs, including magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS), continue to grow as valuable clinical and research tools. Details of existing technology appear abundantly in the literature. For further background material and examples, see the articles and references in the publication by Michael Brant-Zawadzki and David Norman entitled Magnetic Resonance Imaging of the Central Nervous System (published in 1987 by Raven Press Books, Library of Congress No. RC361.5.M34).
Of the various nuclei useful for MRPs, that of phosphorus-31 (P.sub.31) attracts particular attention. Metabolites are present in vivo in the millimolar concentration range needed for convenient observation and they offer a wealth of information. Observed in a P.sub.31 spectrum, various metabolites present an almost ideal picture of real-time processes or energy metabolism taking place in vivo. Further, the relative ratios of various metabolites serve as fingerprints in identifying various organs, tissues, disease states, and even aging. In addition, various ones help determine pH and others help measure the rates of bioenergetic reactions in vivo.
Thus, MRPs promise significant advantages over existing procedures in noninvasively and continuously measuring pH and detecting tissue normoxia and hypoxia. Existing procedures may involve arterial puncture and blood gas analysis, pulmonary artery catheterization and mixed venous O.sub.2 saturation monitoring, and analysis of blood electrolytes and lactic acid level. Beyond the invasive nature of such procedures, pH is subject to change suddenly based on respiratory status, O.sub.2 carrying capacity of blood, and tissue demand and perfusion. In addition, arterial sampling is expensive, potentially dangerous, and time consuming, making results irrelevant to the needs of a patient whose status is changing.
But various problems in existing MRPs need to be overcome to effectively use P.sub.31 for noninvasive and continuous pit and bioenergetics monitoring. For example, the procedure of placing the patient in the bore of a large magnet can be a somewhat unusual and potentially claustrophobic experience. Many seriously ill patients are too unstable to be placed in a large magnet where they are inaccessible to immediate resuscitation. In addition, it may interfere with other procedures the clinician desires to undertake. Furthermore, the cost and complexity of the magnet may be prohibitive, and suitably large facilities to house the magnet and associated equipment may be unavailable. Thus, health care professionals need a better procedure and associated equipment to effectively use P.sub.31 MRS for pH and bioenergetics monitoring.